Recently, technology of connection to the Internet has been drastically advanced. In particular, both wireless communication services of Internet access service having a wide communications service area and low and medium communication data rate (not more than several hundreds kbps), typically cellular type mobile wireless communications system (hereinafter referred to as the “cellular system”) and Internet access service having a local service area (a hot spot area having a diameter of several tens meters or an area of a diameter of several hundreds meters such as shopping mall or urban densely built-up area which is covered by overlapping hot spot areas) and high communication data rate (several tens Mbps), typically wireless local area network (herein after referred to as “WLAN system”) exhibit rapid developments.
The cellular system has features such as wide range and diversity in communication service where as WLAN system has features such as high rate data communication and low charge (fixed charge). In order to effectively use the features of both wireless communications systems, there is a need to merge two different wireless communications systems of cellular type mobile wireless communications system and wireless local area network system and to achieve switching (handoff) therebetween in a seamless manner.
Wireless communications systems which enable a mobile terminal which can be connected and communicated to such two different wireless communications systems to connect each different system and to be seamlessly switched therebetween are proposed in, for example, Japanese Laid-Open Patent Publication No. H09-130405 (pages 13 to 14), Japanese Laid-Open Patent Publication No. 2000-32032 (page 3) and Japanese Laid-Open Patent Publication No. 2002-199426 (pages 5 to 7) In the technology which is disclosed in the above-mentioned specifications, a determination whether or not switching between the wireless communications systems is possible is made based upon the signal strength and signal quality of the receiving signal of the mobile terminal or the position of the mobile terminal and then switching between two different wireless communications systems is conducted. Seamless switching is achieved in such a manner that a user does not perceive the disconnection of communication and the generation of switching between wireless communications systems on switching.
However, the technologies which are disclosed in the above-mentioned specifications do not sufficiently consider the features of each wireless communications system and do not provide communications service which is appropriate and convenient for users, depending upon the conditions of a mobile terminal (for example, the moving speed and communication data rate of the user's mobile terminal). If switching (handoff) between two different wireless communications systems is conducted based upon the signal strength and communication quality of the receiving signal, switching between a plurality of different wireless communications systems is achieved in a seamless manner for a user depending upon the conditions concerning with the signal strength and communication quality of receiving signal. However, appropriate and convenient communications service is not necessarily provided since no condition of the mobile terminal is not considered.
For example, if communication using a WLAN system which covers a local area (hot spot area) is selected when a user moves at a high speed on a highway or Shinkansen, then switching between access points (AP) of WLAN system or WLAN service areas as well as switching between the cellular system and the WLAN system may frequently occur. This may impose excessive burden upon the processing load of the system control of each wireless communications system and the communication processing load of the mobile terminal of a user. As a result, high data rate communication becomes impossible, as well as discontinuation of the communication may occur, so that communication service which is optimum and convenient for the user can not be necessarily provided in some cases.
If the mobile terminal is in the service area which is simultaneously covered by two different wireless communications systems such as WLAN system and cellular system and is connected with the cellular system which covers a wide area so that it is in communication therewith, then switching to WLAN system which is capable of communicating at high communication data rate or at lower charge in a seamless manner is not possible.
As stated in the above, since a high frequency range is used to achieve a high data rate communication in WLAN system, the communication service area is local (range of several hundreds meters at most). In case of cellular system, it is characterized by that the communication data rate is low and medium (several hundreds kbps at most), but the communication service area is wide so that it also covers the communication service area of WLAN system (some areas such as areas in building or underground areas may not be covered).
The prior art which conducts switching (handoff) between two wireless communications systems such as WLAN system and cellular system having foregoing different features depending upon the strength or quality of receiving signal without considering the each feature above may not provide a result which is desirable for the users.
The present invention was made under such circumstances. It is an object of the present invention to provide a wireless communications system, wireless communications method, wireless communications program, and program recording medium in two different communications systems such as a wireless communications system 1 having a wide service area and a low and medium communication data rate, typically cellular system and a wireless communications system 2 having a local service area and a high communication data rate, typically WLAN system, wherein the wireless communications system, wireless communications method, wireless communications program, and program recording medium enable a mobile terminal to select a wireless communications system which is optimum for a user by considering the user's request and mobile terminal conditions such as moving speed or communication data rate of user's mobile terminal, and to connecting the mobile terminal to selected wireless communications system or to continue the communication by conducting switching (handoff) between wireless communications system when the mobile terminal is communicating with another wireless communications system.